Define wavefront. Use Huygen's principle to verify the laws of refraction. How is linearly polarised light obtained by the process of scattering of light?

A) A wavefront is a surface over which an optical wave has a constant.
B) Let AP be the wavefront of the incident wave, of speed in the first medium bev1and in the second medium bev2propagating in the directionAA′incident on the interface at an angle as shown in fig.lettbe time to travel the wavePtoP′, in the same time wavefrontAwill reach atA′,So,As per the diagram,Sini=PP′AP′∴AP′=PP′Sin i. (1)
SimilarlyAP′=AA′Sin r (2)
and,PP′=v1×t
similarlyAA′=v2×t
Now from equation(1)and(2)
v1×t Sin i=v2×t Sin r
SoSin iSin r=v2v1
We know that,n1=cv1 and n2=cv2
SoSin iSin r=n2n1,This is the snell's rule for refraction.
B) When unpolarized light hits a reflective surface, the vertically polarised aspects are refracted into the surface.The horizontally polarised aspects are reflected off the surface and the light is now perceived as partially polarised.When light is reflected, there is an angle at which this light is completely polarised. This is called Brewster's angle, after the Scottish physicist who discovered the law.As per Brewster's ruleμ=tan ib,1.5=tan ib∴ib=tan⁻¹(32)